1. Field of the Invention
Indicating apparatus is provided for indicating the operating state of an electrical component of a load protection system, including a housing containing a longitudinal chamber, an indicating member mounted for longitudinal displacement in the housing chamber, a resilient device normally biasing the indicating member toward a first end of the housing, a catch arrangement for retaining the indicating member in a retracted position adjacent the housing second end; and a release device responsive to a trouble voltage pulse for operating the catch arrangement to a released condition, thereby to release the indicating member for displacement by the resilient device toward an indicating position adjacent the housing first end.
2. Description of Related Art
Electrical systems, for example, electrical installations or electrical lines, are protected against trouble events to ensure trouble-free operation by means of protective devices against impairment of their function and/or against destruction.
These electrical circuits with signaling means can signal at least one functional state, for example, functionally capable or defective, for a protective device. In this way, one can facilitate the checking and/or maintenance of protective devices because an expert entrusted with monitoring does not have to do any measurements on a protective device in order to get information on the functional state of that device. The functional state of a protective device that is to be monitored can be perceived directly by means of signaling action, for example, via optical signaling.
In the context of the present invention, a trouble event is intended to mean an event whose occurrence impacts an electrical system with electrical energy, specifically in such a way that the orderly function of the electrical system is impaired or destroyed. Examples of trouble events are lightning strikes or static discharges, as a result of which, overvoltage pulses and/or over-current pulses are introduced, for example, galvanically, inductively or capacitively into the electrical system, thus impairing or destroying the function of that system. Protective devices against overvoltage pulses have protective elements, among other things, for example, spark gaps, varistors, diodes, suppressor diodes, and are well familiar to the expert. Such protective devices are also referred to as OVP (overvoltage protection).
Furthermore, in the context of this invention, a trouble event is understood to involve a voltage surge with which an electrical system, for example, an electrical power line, can be overloaded and/or destroyed by means of a short circuit or short to ground. Protective devices to provide protection against overvoltage currents are commonly referred to as fuses and are familiar to the expert in many different models, for example, in the form of lead fuses or automatic cutoffs.
Also known are circuits with means for signaling at least one functional state. Reference is made now to FIGS. 3a and 3b to explain such a known circuit of the prior art. Shown is a fuse that connects two electrical forward break points. To signal a functional state of the fuse, there is connected parallel to it a series connection consisting of a voltage multiplier and an opposite parallel circuit consisting of two light diodes. If the fuse is functioning properly, then the voltage prevailing between the two break points will be too small to supply the light diodes with a voltage adequate to get them to light up. If the fuse, for example, is destroyed by an excessively high current and it therefore interrupts the flow of current, then the voltage will rise between the two forward break points and the light diodes will be supplied with adequate voltage in order to signal a defect of the fuse as a functional state lights up in this fashion. It is obvious that, depending on the type of voltage, whether it is direct or alternating voltage, only one or both of the light diodes will light up in each case.
The disadvantage in the known circuits is represented by the fact that the means used for signaling, for example, a light diode, require electrical energy to maintain the signaling function and cause a repercussion on the protective device whose function is to be monitored and/or a facility that supplies electrical energy.
The present invention was developed to solve these problems by an improved electrical protective circuit equipped with signaling means for signaling faulty conditions.